03 Radar Flashcards
ATPL RADIO
What does it mean if a transponder receives a P2 pulse which is stronger than P1 and P3 pulses?
The transponder responses will be suppressed for a short time interval.
When, and from which station, is a Special Position Identification (SPI) pulse sent?
From the aircraft transponder upon selection of the IDENT button by the pilot.
The main factor which determines the minimum range that can be measured by a pulsed radar is pulse:
length
…………………………
The minimum range of a radar is determined by the pulse length (or pulse width). Pulse repetition/recurrence frequency defines the maximum unambiguous range of a radar.
Which of the following equipments works on the interrogator/transponder principle?
Secondary Surveillance Radar (SSR)
……………………….
Secondary surveillance radar (SSR) use a transponder in the aircraft that replies to interrogation pulses from the ground station.
With regard to SSR
the interrogator is on the ground and the transponder is in the aircraft
Surface movement radar operates mainly in the SHF band as opposed to the EHF band. This is because:
EHF is absorbed and scattered by moisture in the air. Use of SHF reduces this problem
When both SSR and primary radar is presented on the controller’s display:
the primary radar information is more accurate in bearing and distance
In an Airborne Weather Radar that has a colour cathode ray tube (CRT) the areas of greatest turbulence are indicated on the screen by:
colour zones being closest together
Which of the following weather returns displayed on an Airborne Weather Radar should be avoided?
Fingers, Hooks, Scallops
Refer to the annex.
On control knob ‘3’, what does ‘MAP’ mode mean?
The ground/terrain will be displayed.
To improve the detection of precipitation area(s) in e.g. thunderstorms, in which the top of the cloud lies at or slightly above the level of flight,
the tilt setting should be lower when the aircraft climbs to a higher altitude.
In which mode of operation does the aircraft weather radar use a cosecant radiation pattern.
MAPPING
………………………….
The airborne weather radar use a cosecant square, fan shaped radiation pattern for ground mapping (up to approximately 70 nm range).
Considering a primary radar system, what kind of aerials are used?
One directional antenna both for transmitting and for receiving.
In order to be able to penetrate cloud, a primary radar signal must have:
a high frequency
What is the maximum number of Secondary Surveillance Radar (SSR) transponder codes in Mode A?
4096
………………………..
The secondary surveillance radar (SSR) transponder has a code selection of 0000 to 7777, where 0 to 7 gives 8 possible numbers, and four digits gives 84 = 4096 combinations.
A ground radar transmitting at a PRF of 1200 pulses/second will have a maximum unambiguous range of approximately:
67 NM
…………………
To find the maximum unambiguous range for a radar based on PRF, the formula to use is:
Maximum Unambiguous Range = Speed of Light / 2 x PRF
MODE S
How does a ground interrogation signal (Mode A and C) get transmitted to a transponder?
in form of pairs of interrogative pulses with an additional control pulse.
In relation to primary radar, what does the term Pulse Recurrence Frequency signify?
The number of pulses transmitted per second.
……………………………………..
Pulse recurrence/repetition frequency (PRF) is the number of pulses transmitted per second. Pulse recurrence/repetition interval (PRI) is the time between two successive pulses.
Which one of the following Secondary Surveillance Radar (SSR) codes should be used by aircraft entering airspace from an area where SSR operation has not been required?
2000
……………………
The SSR code ‘2000’ should be used by aircraft entering airspace from an area where SSR operation has not been required.
Airborne Weather Radar has been primarily developed to detect
the kinds of precipitation which are usually accompanied by turbulence.
A mode A/C transponder receives a P2 pulse from which the amplitude is larger than that of the P1 and P3 pulse. Why is this?
The transonder is located in the direction of one of the side lobes of the interrogator antenna.
Attenuation of radio waves means:
The weakening of the radiated waves
Which of the following equipment uses primary radar principles?
Airborne weather radar (AWR)
A frequency of 10 GHz is considered to be the optimum for use in an airborne weather radar system because:
the larger water droplets will give good echoes and the antenna can be kept relatively small
Ignoring pulse length and fly-back, a radar facility designed to have a maximum unambiguous range of 50 km will have a PRF (pulses per second) of:
3000
In relation to radar systems that use pulse technology, the term ‘Pulse Recurrence Rate (PRR)’ signifies the:
number of pulses per second
When an aircraft is operating its Secondary Surveillance Radar in Mode C an air traffic controller’s presentation gives information regarding the aircraft’s indicated flight level in increments of:
100 FT
………………………..
The transponder will send its altitude information in increments of 100s of feet in mode C.
A moving target indicator:
eliminates all stationary targets
The two main design functions of Secondary Surveillance Radar (SSR) Mode S are:
air to ground and ground to air data link communications and improved ATC aircraft surveillance capability
What information may be displayed on an ATC radar screen connected only to a primary radar system?
Aircraft position only.
……………………………
The primary radar is only able to indicate the position of the aircraft as it only rely on a echo from a target to paint a return without any further exchange of information.
In the Mapping Mode of an airborne weather radar which can utilise two different beam shapes, the:
fan-shaped beam effective up to a maximum of 50 NM to 60 NM range is used.
……………………………
The airborne weather radar use a cosecant square, fan shaped radiation pattern for ground mapping (up to approximately 70 nm range).
What type of beam is used by Airborne Weather Radar in weather mode?
3 – 5º Pencil beam
With SSR, interrogation and response signals:
are standard frequencies separated by 60 MHz
Mode A or C garbling may occur to:
Two or more aircraft in the same direction from the interrogator with a difference in slant range of less than 1.7NM
A weather radar, set to the 100 NM scale, shows a squall at 50NM. By changing the scale to 50 NM, the return on the radar screen should:
increase in area and move to the top of the screen
In Airborne Weather Radar (AWR), the main factors which determine whether a cloud will be detected are:
size of the water drops; wavelength/frequency used
Which statement is correct with respect to selections on the transponder control panel?
With ALT selected a reply in the modes A, C and S can be transmitted.
Which combination of characteristics gives best screen picture in a primary search radar?
short pulse length and narrow beam
The frequency of an SSR ground transmission is:
1030 +/- 0.2 MHz
………………………………………….
The secondary surveillance radar (SSR) will send its interrogation pulses at a frequency of 1030 MHz and the airborne transponder will reply at a frequency of 1090 MHz.
In general the operation of airborne weather radar equipment on the ground is:
only permitted with certain precautions, to safeguard health of personnel and to protect equipment
The selection of code 7500 on an aircraft SSR transponder indicates:
unlawful interference with the planned operation of the flight
…………………..
Transponder code 7500 is the international code for an aircraft experiencing unlawful interference (or hijacking).
The tilt angle of an Airborne Weather Radar (AWR) is set at +4°. If the beam width is 5° and the range of the cloud is 40 NM, what is the approximate height of the cloud above or below the aircraft when the weather return from the cloud just disappears from the screen?
6000 ft
…………………….
Ignoring pulse length, the maximum pulse repetition frequency (PRF) that can be used by a primary radar facility to detect targets unambiguously to a range of 200 NM is: (pps = pulses per second)
405 pps
In which frequency band do most airborne weather radars operate?
SHF
……………………….
Weather radars operate at frequencies of around 10 GHz which is in the SHF range (3 GHz – 30 GHz).
A frequency of airborne weather radar is:
9375 MHz
……………………………
The airborne weather radar normally use frequencies around 9 GHz (9000 MHz).
In an Airborne Weather Radar the areas of greatest turbulence are usually indicated on the screen by:
colour zones of red and magenta
……………………..
Areas of red signify areas of large droplets/wet particles indicating possible strong currents of air. For weather radars with turbulence detection, magenta will be used to indicate areas of possible turbulence/windshear within the cloud and also outside, based on the relative movement of the water droplets.
In an Airborne Weather Radar that has a colour cathode ray tube (CRT) increasing severity of rain and turbulence is generally shown by a change of colour from:
green to yellow to red
……………………………………….
Airborne weather radars will indicate the intensity of the precipitation or the size of the droplets as a range of colours, ranging from weaker to stronger:
- Green
- Yellow/amber
- Red
- Magenta
The “gain” control knob of an AWR adjusts:
the receiver sensitivity in order to achieve optimum target acquisition.
……………………………
The gain control of an airborne weather radar is used to adjust the sensitivity of the radar receiver and the higher the gain, the greater the sensitivity, i.e. any returns will be shown at a greater severity.
Which one of the following switch positions should be used when selecting a code on the transponder?
STBY (Standby)
…………………………….
It is common practice to switch a transponder to STBY (Standby) before selecting a new SSR code.
In weather radar the use of a cosecant beam in ‘Mapping’ mode enables:
scanning of a large ground zone producing echos whose signals are practically independent of distance
MODE S
The allocation of 24-bit aircraft addresses is described in ICAO annex 10, it states that:
every aircraft will have been allocated with an ICAO Aircraft Address which is hard coded into the airframe.
A Primary radar operates on the principle of:
pulse technique
……………………………….
Primary radar work on the principle of transmitting a pulse and receiving an echo back from a reflection of the pulse that was sent out. The amount of reflection depends on the frequency of the pulse and the nature of the object that created the reflection.
Which answer is correct concerning information determined and shown by ATC PSR (Primary Surveillance Radar) and SSR (Secondary Surveillance Radar) systems?
PSRs determine and show target range and bearing. SSRs determine and show target range, bearing, aircraft identification codes, aircraft altitude, selective addressing and full two-way data link.
The receiver in a primary radar:
all answers are correct
The magnetic heading of an aircraft is 040°. On the Airborne Weather Radar display the relative bearing of and the distance to the most southerly part of Lands End (approximate position: 50°03’N , 005°40’W) are, 030°R and 80 NM.
What is the position of the aircraft based on these observations?
The slant range correction and the map convergency between aircraft position and Lands End may be neglected.
(49°25’N , 007°30’W)
On the airborne weather radar display in WX mode, different colours are used:
to display different intensity of precipitation
The Moving Target Indication (MTI) in a primary radar has the following function:
Erase all stationary targets.
In a primary radar using pulse technique, the ability to discriminate between targets in azimuth is a factor of:
beam width
On a typical computer generated SSR display the following data on a particular flight will be shown:
squawk code, flight level, ground speed, airplane callsign
The antennae of modern airborne weather radars are stabilized by means of:
inputs from the aircraft’s attitude system.
In SSR, the interrogations use different modes. If altitude reporting is required, the aeroplane’s transponder should be set to “ALT” and will respond to:
Mode C and A interrogations
What determines the operating mode (A or C) of the SSR transponder?
The time interval between the pulses P1 and P3.
The maximum range of primary radar depends on:
pulse recurrence frequency
A side lobe from the aerial of a weather radar may produce an echo on the screen known as a “height ring”. The pilot can use this:
to determine that the weather radar is functioning
A TCAS II equipped a/c will have mode S because:
the datalink is required to co-ordinate evasive manoeuvres
What are the frequencies used for interrogation and response for SSR?
1030 MHz for interrogation from the ground, 1090 MHz for response from the aircraft
Echoes that do not change in distance from the antenna (relative speed zero) of a ground radar with a Moving Target Indicator (MTI) are dangerous for the following reason
The moving target indicator (MTI) eliminates such echoes.
When using airborne weather radar in the mapping mode in polar areas one runs the risk
of mistaking the edge of coastal ice off shore for the real coastline.
In a primary pulse radar you have:
a directional aerial for both transmission and reception
On which of the following radar displays is it possible to get an indication of the shape, and to some extent the type, of the aircraft generating the return?
Aerodrome Surface Movement Radar (ASMR)
Why is a secondary radar display screen free of storm clutter?
The principle of ‘echo’ return is not used in secondary radar
An airborne weather radar (AWR) transmits a pulse with a wavelength of approximately 3.2 cm, what is the corresponding frequency?
9.375 GHz
The maximum range obtainable from an ATC Long Range Surveillance Radar is approximately:
200-300 NM
A mode A/C transponder receives a P2 pulse, the amplitude of which is smaller than that of the P1 and P3 pulse. What is the reason?
The transponder is located in the direction of the main lobe of the interrogator antenna.
In the MAPPING MODE the airborne weather radar utilises a:
fan shaped beam effective up to a maximum of 50 NM to 60 NM range
The minimum range of a primary radar, using the pulse technique, is determined by the (i)…….. ; the maximum unambiguous range by the (ii)………
(i) pulse length (ii) pulse recurrence frequency
………………………..
The minimum range of a radar is determined by the pulse length (or pulse width). Pulse repetition/recurrence frequency defines the maximum unambiguous range of a radar.
With mode-S each aircraft can be uniquely interrogated and identified by using the
24 bits address code, giving more than 16 million possible codes.
The tilt angle of an Airborne Weather Radar (AWR) is set at +6°. If the beam width is 4° and the range of the cloud is 30 NM, what is the approximate height of the cloud above or below the aircraft when the weather return from the cloud just disappears from the screen?
12 000 ft
For a primary radar system an aerial with a high rotation rate means that:
target information is rapidly refreshed
In a primary radar using pulse technique, pulse recurrence frequency (PRF)/pulse recurrence rate (PRR) determines:
maximum theoretical range
Under CS-25 colour code rules for Electronic Flight Instrument Systems (EFIS), increasing intensity of precipitation are coloured in the order:
green, amber/yellow, red, magenta
The maximum pulse repetition frequency (PRF) that can be used by a primary radar facility in order to detect targets unambiguously at a range of 50 NM is: (pps = pulses per second)
1620 pps
……………………..
Maximum Unambiguous Range = Speed of Light / 2 x PRF
In order to indicate radio failure the aircraft SSR transponder should be selected to code:
7600
Which of the following types of shapes depicted on an Airborne Weather Radar (AWR) display should be avoided?
Fingers, Hooks, Scallops
When an operator increases the range on a radar-display, in general,
the PRF becomes lower and the pulse length larger.
Refer to the annex.
Making the selection ‘WX + T’ on control knob ‘3’ will display:
weather and turbulence.
What is the function of pulse P2 in mode A/C-interrogation?
To avoid responses from aircraft which are located in the direction of the side lobes of the interrogator antenna.
What is the maximum theoretical unambiguous range for a primary radar with a PRF of 500 pps?
300 km
Which one of the following is an advantage of a secondary radar system when compared to a primary radar system?
The required power of transmission from the ground equipment is reduced.
Garbling is caused by:
aeroplanes in close proximity responding to the same interrogation
A secondary radar can provide up to 4096 different codes. These 4096 codes can be used in:
all modes
In the SSR terminology “de-fruiting” means:
the removal from the display of random responses
What is the term used for situations when a specific SSR ground station receives reply pulses from an aircraft which are caused by interrogations from a different SSR ground station?
Fruiting
Garbling in mode A and C may occur:
when two or more aircraft are in approximately the same direction from the interrogator with a difference in slant range of less than 1.7 NM.
In order to indicate unlawful interference with the planned operation of the flight, the aircraft Secondary Surveillance Radar (SSR) transponder should be selected to:
7500
Airborne weather radar systems use a wavelength of approximately 3 cm in order to:
detect the larger water droplets
Which of the following groups of shapes on an airborne weather radar display should be avoided?
Fingers, Hooks, Scallops
Which of the following lists the phenomena least likely to be detected by radar?
clear air turbulence
In a primary radar using pulse technique, pulse length determines:
minimum measurable range
An airborne weather radar (AWR) transmits a pulse with a wavelength of approximately 3.12cm. What is the corresponding frequency?
9 380 MHz
The code transmitted by a SSR transponder consists of:
pulses
Ignoring pulse length, the maximum pulse repetition frequency (PRF) that can be used by a primary radar facility to detect targets unambiguously to a range of 125 NM is:
648 pps
The theoretical maximum range for an Airborne Weather Radar is determined by the:
pulse recurrence frequency
The pictures at reference are showing an aircraft’s position with respect to some thunderstorm cells and the image the pilot is getting from the radar. To detect this “blind alley” the pilot should
increase the range setting of his radar.
The selection of code 7700 on an aircraft SSR transponder indicates:
an emergency
Refer to the annex.
Changing the gain on control knob ‘1’ will change the:
sensitivity of the receiver.
When using the airborne weather radar equipment on the ground before take-off:
the radar transmitter should not be operated when personnel is observed in the sector ahead of the aircraft
Which statement relating to the stabilization of airborne weather radar antennae is true?
They are stabilized with respect to the pitch and roll axis but not with respect to the yaw-axis.
The PRF of a primary pulse radar is 500. Its maximum unambiguous range in NM is approximately:
160 NM ................................ The maximum range of a pulse radar system is determined by its Pulse Repetition Frequency (PRF), also known as the Pulse Recurrence Rate (PRR). It is calculated using the formula: Maximum Range = Speed of Light / 2 x PRF
The maximum range of a pulse radar is affected by:
All of these
……………..
Transmission frequency, Pulse width, PRP
The ATC transponder system, excluding Mode S, contains :
two modes, each of 4096 codes.
The ground Secondary Surveillance Radar (SSR) equipment incorporates a transmitter and receiver respectively operating in the following frequencies: Transmitter Receiver
1030 MHz 1090 MHz
The airborne weather radar uses the following wavelengths:
centimetric.
In order to ascertain whether a cloud return on an Aircraft Weather Radar (AWR) is at or above the height of the aircraft, the tilt control should be set to: (Assume a beam width of 5°)
2.5° up
Which describes the correct tilt setting for a weather radar?
During a climb, the tilt needs to be decreased to scan for hazardous clouds.
The pencil shaped beam of an airborne weather radar is used in preference to the mapping mode for the determination of ground features:
beyond 50 to 60 NM because more power can be concentrated in the narrower beam
Using SSR, the normal transmission from the ATC transponder in the aircraft consists of:
the aircraft identification plus pulses giving the altitude
Which of the following radar equipment operate by means of the pulse technique? 1. Aerodrome Surface Movement Radar 2. Airborne Weather Radar 3. Secondary Surveillance Radar (SSR) 4. Aerodrome Surveillance (approach) Radar
1, 2, 3 and 4
Which of the following is a complete list of airborne weather radar antenna stabilisation axes?
roll and pitch
“Fruiting” is caused by:
aeroplane at range responding to interrogations from another ATC radar station
When the airborne weather radar is operating in its primary (WX) mode, to detect precipitation
the radar beam is pencil-shaped
A mode S transponder receives among other pulses a long P4 pulse from an interrogator. What does this mean?
The interrogator transmits a Mode A/C/S all call.
Which radar system is used to detect aircraft that are not equipped with an operational transponder?
PSR (Primary Surveillance Radar).
Complete the following statement. Aircraft Surface movement Radar operates on frequencies in the (i) ………. band employing an antenna that rotates at approximately (ii) ………. revolutions per minute; it is (iii) ……… possible to determine the type of aircraft from the return on the radar screen.
(i) SHF (ii) 60 (iii) sometimes
Which of the following types of radar systems are most suited for short range operation?
Primary continuous wave
Assuming sufficient transmission power, the maximum range of a ground radar with a pulse repetition frequency of 450 pulses per second is: (Given: velocity of light is 300 000 km/second)
333 km
……………………..
To find the maximum unambiguous range for a radar based on PRF, the formula to use is:
Maximum Unambiguous Range = Speed of Light / 2 x PRF
Which of the following lists the phenomena least likely to be detected by radar?
clear air turbulence
In order to indicate an emergency situation, the aircraft Secondary Surveillance Radar (SSR) transponder should be set to:
7700
When the ATC transponder “IDENT” button is pressed by the pilot:
the airplane’s symbol on the controller’s display will flash or “fill in”
Airborne weather radars are generally based on the use of:
primary radar in the SHF band
A mode S transponder receives among other pulses a short P4 pulse from an interrogator. What does this mean?
The interrogator transmits a mode A/C only all call.
A mode S transponder:
responds normally to mode A or C interrogations
Which of the following cloud types is most readily detected by airborne weather radar?
cumulus
The selection of code 7600 on an aircraft SSR transponder indicates:
radio communication failure
What causes garbling in SSR?
A phenomenon that happens at the ground receiver due to superimposition of two replies from different transponders.
The ISO-ECHO facility of an airborne weather radar is provided in order to:
detect areas of possible severe turbulence in cloud
Which statement with respect to interrogation modes is correct?
Mode S Broadcast will transmit information to all mode S transponders.
When Mode C is selected on the aircraft SSR transponder the additional information transmitted is:
flight level based on 1013.25 hPa
For any given circumstances, in order to double the effective range of a primary radar the power output must be increased by a factor of:
16
How does a Mode S interrogator identify aircraft?
a 24 bit identifier, giving over 16 million combinations.
The prime factor in determining the maximum unambiguous range of a primary radar is the:
pulse recurrence rate
The heaviest turbulence is likely to be encountered
where the area of heaviest precipitation is closest to the edge of the thunderstorm cell.
Which one of the following statements is correct concerning the use in primary radar of continuous wave transmissions as compared with pulse transmissions?
It eliminates the minimum target reception range
The spacing between the two pulses transmitted by an SSR interrogator determines:
what mode is used
When the Airborne Weather Radar (AWR) is operating in the weather (WX) mode the following type of beam is used:
3 - 5° Pencil beam
